1. Field of the Invention
The present invention relates to a lens barrel which is variable in a barrel length between a storage state relatively short in a barrel length and an image taking state relatively long in a barrel length, and a camera having such a lens barrel.
2. Description of the Related Art
Hitherto, such a type of camera that photography is performed on a silver halide film comes into wide use. And recently, in addition to such a type of camera, there rapidly comes into wide use an electronic camera in which a subject is image-formed on a solid state imaging device such as a CCD imaging device to derive image data representative of the subject. The camera of such a type that photography is performed on a silver halide film and the electronic camera as mentioned above are simply referred to as a xe2x80x9ccameraxe2x80x9d.
Generally, a camera requires a high order of portability. And thus there is widely used a collapse and extension type of lens barrel arranged in such a manner that a lens barrel holding an image taking lens is collapsed into a camera body side when the camera is not used, and the lens barrel projects from the camera body side ahead when photograph is performed. Also in the conventional so called-compact camera and the recent electronic camera, there are widely used a lens shutter and an aperture disposed between image taking lenses.
In the lens barrel variable in collapse and extension and a camera provided with the lens shutter and the aperture, as mentioned above, it is a problem as to how the portability is improved.
In this case, as one of points contributing to an improvement of the portability, there may be raised thinness of a lens barrel at the time of collapse in an optical axis direction.
FIG. 17 is a sectional view of a lens barrel of the conventional camera at the time of collapse taken along optical axis S.
FIG. 17 shows a collapse and extension type of lens barrel 10. The lens barrel 10 comprises an image taking lens 20 consisting of a first group lens 21, a second group lens 22 and a third group lens 23, and a lens shutter 30 disposed between the first group lens 21 and the second group lens 22 of the image taking lens 20. The lens barrel 10 is of a zoom lens structure capable of adjusting a focal length at the time of extension as well as permission of collapse and extension. At the rear portion of the lens barrel 10, there is disposed a CCD imaging device 40 which is fixed on a camera body side. That is, here, there is shown a lens barrel 10 for an electronic camera.
As shown in FIG. 17, of the lens groups constituting the image taking lens 20, the second group lens 22 and the third group lens 23 are disposed at mutually very closed positions in the collapsed state shown in FIG. 17. However, between the first group lens 21 and the second group lens 22, there is the lens shutter 30, and thus the first group lens 21 and the second group lens 22 are disposed away from one another to some extent putting the lens shutter 30 therebetween. This makes it impossible to reduce the size of the lens barrel at the time of the collapse.
For example, Japanese Patent Laid Open Gazette Hei. 6-258702 discloses a camera in which a photographic optical system of a single focal point comprising a plurality of lens groups is movable between an initial position for a photography and a collapsed position saved from the initial position to a camera main body side, wherein the camera has a mechanism that when the photographic optical system is moved to the collapsed position, the plurality of lens groups is reduced in interval among the lens groups as compared with that of the initial position so that the length of occupation of the photographic optical system is altered.
Further Japanese Patent Laid Open Gazette Hei. 10-288731 discloses a zoom lens, which is miniaturized by improvement of an aperture driving mechanism. However, this is not to solve the problems of the aperture and the shutter per se. And thus, there is a limit of miniaturization.
In view of the foregoing, it is an object of the present invention to provide a lens barrel capable of reducing a size (a barrel length) in an optical axis direction as compared with the conventional lens barrel which is variable in a barrel length between a collapsing state and an extension state, and also provide a camera provided with such a lens barrel.
To achieve the above-mentioned objects, the present invention provides a lens barrel which is variable in a barrel length between a storage state relatively short in a barrel length and an image taking state relatively long in a barrel length, wherein the lens barrel incorporates therein a image taking lens consisting of a plurality of lens groups, the lens barrel comprising:
a light quantity control member which is in a use state that a light quantity of a photographic light passing through the image taking lens is controlled, when the lens barrel is in the image taking state, and which is in a non-use state that an opening is kept on a predetermined aperture size; and
a lens movement mechanism that moves at least part of members constituting any lens group of the plurality of lens groups constituting the image taking lens to a state that the part comes into the opening of the light quantity control member, when the lens barrel moves from the image taking state to the storage state.
In the lens barrel according to the present invention as mentioned above, it is acceptable that the light quantity control member is a lens shutter or an aperture member. Alternatively, it is acceptable that the light quantity control member is a member used both as a lens shutter and an aperture member.
According to the lens barrel of the present invention, at least part of members constituting any lens group of the plurality of lens groups constituting the image taking lens is moved to a state that the part comes into the opening of the light quantity control member, when the lens barrel moves from the image taking state to the storage state. This feature makes it possible to reduce the barrel length in the storage state as compared with the conventional one.
In the lens barrel according to the present invention as mentioned above, it is preferable that when the light quantity control member is in the non-use state, the light quantity control member maintains the opening in an opening state that the opening is opened more than a maximum aperture in the use state.
There is a need to determine the maximum aperture in the image taking state from the viewpoint of the image taking efficiency. The size of the maximum aperture in the image taking state is not always an aperture size sufficient for accommodating at least part of members constituting any lens group of the plurality of lens groups in the opening of the light quantity control member, at the time of the storage state. In this case, when the lens barrel is in the storage state, the light quantity control member maintains the opening in an opening state that the opening is opened more than a maximum aperture in the image taking state. Thus, it is possible to satisfy both the image taking ability and the storage ability.
In the lens barrel according to the present invention as mentioned above, it is preferable that the lens barrel further comprises a compulsory changing over member that forcibly changes over the light quantity control member to the non-use state, before the part is in contact with the light quantity control member, when the lens barrel moves from the image taking state to the storage state.
Even if a malfunction of the lens control system or a mechanical shock in operation bring about an approach of the lens groups to the light quantity control member, the presence of the compulsory changing over member makes it possible to avoid a mechanical destroy of the lens barrel since the light quantity control member moves to the non-use state.
In the lens barrel according to the present invention as mentioned above, it is preferable that the compulsory changing over member is a rod-like shaped member projecting toward the light quantity control member provided on a side of the lens groups, and
the light quantity control member is in contact with the compulsory changing over member, before the part is in contact with the light quantity control member, when the lens barrel moves from the image taking state to the storage state, so that the light quantity control member changes over to the non-use state upon receipt of a driving force wherein the lens barrel moves to the storage state, via the compulsory changing over member.
The use of the rod-like shaped member makes it possible to avoid a possibility that the lens groups are in contact with the light quantity control member, and also possible to readily change over the light quantity control member to the non-use state in accordance with the movement of the lens barrel to the storage state.
In the lens barrel according to the present invention as mentioned above, it is preferable that the lens barrel further comprises control means that maintains the non-use state wherein the light quantity control member withdraws to a predetermined withdrawal position, when the lens barrel is in the storage state, and controls an approach of the lens groups to the light quantity control member in an optical axis direction, when the light quantity control member is in a non-withdrawal position.
In the lens barrel according to the present invention as mentioned above, it is acceptable that the control means comprises an engagement member provided on a side of the lens groups, and a control member that comes into a movement path for the engagement member from out of the movement path in connection with a movement of the light quantity control member from the withdrawal position to the non-withdrawal position, and the control member is constructed in such a manner that before at least part of the lens groups is in contact with the light quantity control member at the non-withdrawal position, the control member is in contact with the engagement member to prevent contact of the part with the light quantity control member.
In the lens barrel according to the present invention as mentioned above, it is acceptable that the light quantity control member consists of an aperture blade, and the control member is constructed in united body with the aperture blade.
It is acceptable that there is provided such an arrangement that the control member withdraws from inside a movement path for the engagement member to outside the movement path at the time of the shutter open in connection with a movement of the shutter blade.
To achieve the above-mentioned objects, the present invention provides a camera having a lens barrel that holds a image taking lens consisting of a plurality of lens groups, and a light quantity control member for controlling an amount of light passing through the image taking lens, the lens barrel being variable in a barrel length between a storage state relatively short in a barrel length and an image taking state relatively long in a barrel length, wherein a photography is carried out by a photographic light passing through the light quantity control member,
wherein the lens barrel maintains at least part of members constituting any lens group of the plurality of lens groups constituting the image taking lens to a state that the part comes into the opening of the light quantity control member, when the lens barrel is in a storage state.
In the camera according to the present invention as mentioned above, it is acceptable that the light quantity control member is a lens shutter or an aperture member. Alternatively, it is acceptable that the light quantity control member is a member used both as a lens shutter and an aperture member.
According to the camera of the present invention as mentioned above, the lens barrel maintains at least part of members constituting any lens group of the plurality of lens groups constituting the image taking lens to a state that the part comes into the opening of the light quantity control member, when the lens barrel is in a storage state. This feature makes it possible to reduce the size of the lens barrel at the time of the collapse as compared with the conventional one, and thus, it is possible to provide a thin type of camera excellent in portability.
In case of an electronic camera, there is no problem on a point that when the lens barrel is in the storage state, it is set to a state that light may passes through the light quantity control member. However, in case of the conventional type of camera that photography is carried out on a silver halide film, setting to the state that light may passes through the light quantity control member involves a possibility that the silver halide film is exposed with the light passing through the light quantity control member. But, this problem is concerned with when no measures is taken, and this problem can be solved in accordance with provision of, for example, a lens cover, a front cover or a lens barrier, which are excellent in a light shielding property, or provision of a focal plane shutter.
That is, the present invention is applicable to not only the electronic camera, but also the conventional type of camera that photography is carried out on a silver halide film.
In the camera according to the present invention as mentioned above, it is acceptable that when the lens barrel is in the storage state, the light quantity control member maintains an opening in an opening state that the opening is opened more than a maximum aperture in the image taking state.
There is a need to determine the maximum aperture in the image taking state from the viewpoint of the image taking efficiency. The size of the maximum aperture in the image taking state is not always an aperture size sufficient for accommodating at least part of members constituting any lens group of the plurality of lens groups in the opening of the light quantity control member, at the time of the storage state. In this case, when the lens barrel is in the storage state, the light quantity control member maintains the opening in an opening state that the opening is opened more than a maximum aperture in the image taking state. Thus, it is possible to satisfy both the image taking ability and the storage ability.
In the camera according to the present invention as mentioned above, it is preferable that the light quantity control member is free in changing over of states between a use state that a light quantity of a photographic light passing through the image taking lens is controlled and a non-use state wherein it is permitted that at least part of members constituting any lens group of the plurality of lens groups constituting the image taking lens comes into an opening of the light quantity control member, and when the lens barrel is in the image taking state, the light quantity control member is in the use state to control a light quantity of a photographic light passing through the image taking lens, and
the camera further has a compulsory changing over member that forcibly changes over the light quantity control member to the non-use state, before the part is in contact with the light quantity control member, when the lens barrel moves from the image taking state to the storage state.
Even if a malfunction of the lens control system or a mechanical shock in operation bring about an approach of the lens groups to the light quantity control member, the presence of the compulsory changing over member makes it possible to avoid a mechanical destroy of the lens barrel since the light quantity control member moves to the non-use state.
In the camera according to the present invention as mentioned above, it is preferable that the compulsory changing over member is a rod-like shaped member projecting toward the light quantity control member provided on a side of the lens groups, and
the light quantity control member is in contact with the compulsory changing over member, before the part is in contact with the light quantity control member, when the lens barrel moves from the image taking state to the storage state, so that the light quantity control member changes over to the non-use state upon receipt of a driving force wherein the lens barrel moves to the storage state, via the compulsory changing over member.
The use of the rod-like shaped member makes it possible to avoid a possibility that the lens groups are in contact with the light quantity control member, and also possible to readily change over the light quantity control member to the non-use state in accordance with the movement of the lens barrel to the storage state.
In the camera according to the present invention as mentioned above, it is preferable that the lens barrel further comprises control means that maintains the non-use state wherein the light quantity control member withdraws to a withdrawal position wherein it is permitted that at least part of members constituting any lens group of the plurality of lens groups constituting the image taking lens comes into an opening of the light quantity control member, when the lens barrel is in the storage state, and controls an approach of the lens groups to the light quantity control member in an optical axis direction, when the light quantity control member is in a non-withdrawal position.
In the camera according to the present invention as mentioned above, it is acceptable that the control means comprises an engagement member provided on a side of the lens groups, and a control member that comes into a movement path for the engagement member from out of the movement path in connection with a movement of the light quantity control member from the withdrawal position to the non-withdrawal position, and the control member is constructed in such a manner that before at least part of the lens groups is in contact with the light quantity control member at the non-withdrawal position, the control member is in contact with the engagement member to prevent contact of the part with the light quantity control member.
In the camera according to the present invention as mentioned above, it is acceptable that the light quantity control member consists of an aperture blade, and the control member is constructed in united body with the aperture blade.
It is acceptable that there is provided such an arrangement that the control member withdraws from inside a movement path for the engagement member to outside the movement path at the time of the shutter open in connection with a movement of the shutter blade.